2B_Kel.3 Video Praktikum Bakteriologi | Uji Reduksi Nitrat, Uji Mr-Vp, Uji Sitrat, dan Uji Gula-gula

Summary

This video, presented by Group 3 from the Bacteriology 2 course, guided by Bunda Putri Widellia Williana, demonstrates various bacterial biochemical tests, including nitrate reduction, MRPV, citrate, and sugar fermentation tests. The nitrate reduction test shows how bacteria reduce nitrate to nitrite or ammonia, while the MRPV test checks carbohydrate fermentation and acid production. The citrate test identifies bacteria's ability to use citrate as a carbon source. Lastly, the sugar fermentation test reveals if bacteria can ferment sugars. The video explains detailed procedures and results interpretation for each test.

Takeaways

• 🧪 The group is from a bacteriology class taught by Bunda Putri Widelia Williana, focusing on various biochemical tests.
• 🔬 The first test, nitrate reduction, aims to determine bacteria's ability to reduce nitrate to nitrite or ammonia, simulating anaerobic conditions.
• 🦠 Materials used in the nitrate reduction test include cultures of Streptococcus thermophilus, Escherichia coli, Bacillus subtilis, and reagents like sulfanilic acid and Alpha-naphthylamine.
• 🧼 The procedure involves sterilizing the work area and tools with 70% alcohol before inoculating the bacteria into nitrate broth and incubating at 37°C for 2 days.
• 🔍 After incubation, reagents are added to detect nitrate reduction, and results are observed based on color changes.
• 🧪 The second test, MR-VP, checks for the production of organic acids from glucose fermentation. Methyl red is used to indicate pH changes, with red being positive and yellow/orange negative.
• 🧪 The VP (Voges-Proskauer) test checks for acetoin production using Alpha-naphthol and KOH, with a red color indicating a positive result.
• 🧪 The third test, citrate utilization, determines whether bacteria can use citrate as a carbon source. A color change to blue indicates a positive result, while green indicates negative.
• 🧪 The fourth test, sugar fermentation, involves inoculating bacteria into sugar media. A yellow color change indicates positive fermentation of the sugar.
• 📜 The group demonstrates the preparation of media and the procedure for all four tests, emphasizing aseptic techniques and proper incubation times.

Q & A

What is the purpose of the nitrate reduction test?

The purpose of the nitrate reduction test is to determine the biochemical ability of bacterial cultures to reduce nitrate to nitrite or ammonia, which indicates anaerobic respiration capabilities.

What materials are required for the nitrate reduction test?

The materials needed for the nitrate reduction test include a micropipette, ose loop, Bunsen burner, 70% alcohol, Streptococcus thermophilus, Escherichia coli, Bacillus subtilis, sulfanilic acid, alpha-naphthylamine, and sodium broth medium.

How is the MR-VP test performed, and what does it determine?

The MR-VP test involves adding methyl red to bacterial cultures grown on MR-VP media to detect the presence of mixed acid fermentation by observing color changes. It also uses alpha-naphthol and KOH to check for acetoin production, which helps distinguish bacterial pathways for glucose metabolism.

What are the possible outcomes of the methyl red (MR) test?

The possible outcomes of the MR test are red (positive, indicating acidic fermentation), orange (intermediate pH between 4.4 and 6.2), and yellow (negative, indicating no acid production).

What is the significance of color changes in the VP test?

A red color change in the VP test indicates a positive result for acetoin production, signifying that the bacteria can ferment glucose into neutral end products. A lack of color change indicates a negative result.

How is the citrate test conducted, and what does a positive result look like?

In the citrate test, bacterial samples are inoculated on citrate agar and incubated for 24 hours. A positive result turns the medium blue, indicating citrate utilization. A green color means citrate was not utilized, giving a negative result.

What is the purpose of the Durham tube in the sugar fermentation test?

The Durham tube is used to capture any gas produced during fermentation. If gas is present, it forms a bubble in the inverted tube, indicating that fermentation produced gas as a byproduct.

What does a color change to yellow signify in the sugar fermentation test?

A color change to yellow indicates that the bacteria have fermented the sugar in the medium, lowering the pH due to the production of acidic byproducts.

Why is the workspace sterilized with 70% alcohol before beginning the tests?

The workspace is sterilized with 70% alcohol to minimize contamination and ensure an aseptic environment for accurate testing.

What is the incubation temperature and duration for the various tests discussed?

For nitrate reduction, MR-VP, citrate, and sugar fermentation tests, the incubation temperature is set to 37°C, with durations generally ranging from 18 to 24 hours.